Flat-bank crossbar switch



Dec. 4, 1956 E. L. EARLE @2,773929 FLAT-BANK cRossBAR SWITCH me@ July27, 1955- 2 sheets-sheet 1 Dec. 4, 1956 E. EARLE 2,773,129

FLAT-BANK CROSSBAR SWITCH Filed July 27, 1955- 2 Sheets-Sheet 2 FIG. 2

|53 INSULATION |53 FIG. 3

INSULATION |32 FLAT-BANK CROSSBAR SWITCH Edwin L. Earle, Chicago, lil.,assignor to International Telephone and Telegraph Corporation, New York,N. Y., a corporation of Maryland Application July 27, 1955, Serial No.524,632

3 Claims. (Cl. 179-2754) This invention relates to a at-bank crossbarswitch such as is used in automatic telephone systems and elsewhere. Theprincipal object of the invention is to provide an improved constructionfor the contact bank and for the crosspoint-actuating mechanism of thenoted type of switch which simplies the adjustment procedure whileavoiding the likelihood of undesired circuit closures by crosspointcontact members in their normal relaxed position.

The at-bank crossbar switch is exemplified by the United States PatentNo. 2,577,067, issued December 4, 1951. ln such a crossbar switch, theexible contact members of the stacks used at the crosspoint extendparallel to the plane of the switch frame, rather than at right anglesthereto, thus enabling the horizontal multiple, in addition to thevertical multiple, to be built in as a part of the bank construction.

Heretofore, the crosspoint contact members of the contact bank of such aswitch have required careful adjustment to insure their eifectiveopening on release while preventing retraction to an extent suicient tomake unwanted metallic contact with the xed contact members associatedwith the underlying flexible Contact members. Moreover, a ratherexpensive backstop arrangement external to the contact bank has beenrequired to maintain the crosspoint actuators, or ladders, at a commonlevel for free crosspoint selection with a minimum of lost actuatingmovement.

According to the invention, the two foregoing dii-liculties have beensimply and economically overcome by widening certain of the insulatingstrips already required in the several clamping assemblies to precludethe unwanted metallic contact of released ilexible Contact members,which provides an insulated surface which serves the dual purpose of (l)preventing unwanted electrical contact, and of (2) providing a denitestopping position for the actuating ladders. Preferably, the flexiblecontact blades have no denite opening tension formed therein, and therequired opening tension is supplied by a separate spring bladeoverlying each stackup.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent, and theinvention itself will be best understood, by reference tothe followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings comprising Figs. l to 3, wherein:

Fig. l is a top view of a switch embodying the invention;

Fig. 2 is a sectional view, taken along line 2-2 of Fig. l; and

Fig. 3 is a partial sectional view similar to Fig. 2, showing a modifiedconstruction.

Figs. 1 and 2 Referring rst to Fig. l, the improved crossbar switchshown therein comprises a contact bank providing the desired number andarrangement of stackups, together United States Patent O ICC with arectangular structure for supporting the contact bank and controllingthe desired actuation of the stackups thereof. The rectangular structuremay be constructed generally as is disclosed in the noted patent. Such astructure includes front and rear members 1 and 3, and left and rightframe members 2 and 4 suitably secured thereto through corner .gussets 5and 6, six horizontal select shafts, S1-2 to SIL-12, pivotally mountedbetween shaft brackets 18 and 19, a desired number of vertical bars orhold-magnet armatures 90, pivotally mounted between front and rearmembers 1 and 3, and a contact bank providing stackup comprisingvertical rows overlying the respective armatures 90, the contact bankbeing supported on channels 25.

The front frame member 1 is provided with an inwardly extending upperange. The rear member 3 is a similar structure, but with an inwardlyextending lower ange added. The upper flanges of both members serve asmounting supports for members 25 while the lower ilange on rear member 3serves as a mounting support for hold-magnets 80.

Shaft brackets 18 and 19, extend across the switch frame at the ends,and are suitably secured to corner gussets 5 and 6. These bracketssupport the select shafts S1-2 to S11-12, and their associated selectmagnets M1 to M12 as described more fully in the noted patent.

Channels 25 are secured to the upper anges of front rear members 1 and 3by screws 26. Elongated apertures 221 permit channels 25 to beadjustably aligned. Each clamping stackup 150 is secured to a channel 25by screws 153 which pass through the stackup and are threadedly engagedin tapped holes 27. Pilot holes 29 are provided in channels 25 which maybe used during assembly of the bank for alignment of the parts.

A hold-magnet and associated armature 90 are provided for each verticalrow of contact stackups. Hold magnets 80 are adjustably mounted upont-he lower flange of rear frame member 3 below and slightly to the leftof their associated stackups. Armature 90, extending from rear framemember 3 to front frame member 1, are pivotally mounted at each end topermit their rotation to actuate selected stackups of contacts.

Mounting tab 93 of a-rmature 90 is pivotally secured to the rear framemember 3 by bearing pin 109 and is pivotally secured to the front framemember 1 by adjustable armature leveling plate 112. As disclosed in thenoted patent, the exposed face of the front member 1 is provided withelongated openings to receive an adjustable armature leveling assemblywhich is secured thereto by a screw. The leveling assembly includes abearing screw 206 which is threaded through plate 112 to engage armaturemounting tab 93 to support and to provide lateral adjustment of armature90. A slot in the end of bearing screw 206 facilitates this adjustmentand locknut 209 locks the bearing screw in its adjusted position.Armature is readily removed by loosening locknut 209, backing outbearing screw 206, disengaging bearing pin 109 and dropping the armatureout of the switch structure.

The armature 90 comprises a tractive portion 91 which overlies the upperend of the core of its associated holdrnagnet 80 and a laterallyextending main portion 92 which carries pivotally secured select levers220. The main portion 92 has its edge portion 94 turned up to provide amore rigid structure. An adjustable platform 95 is provided for eachpair of adjacent crosspoints, being integrally connected with the mainportion 92 by arms 96. Each structure 95 includes a recess 213, thesides of which engages the select-lever downwardly extending tab 219(Fig. 2) to provide a stop position for select lever 220.

The construction of the contact bank supported on channels 25, toprovide the vertical and horizontal rows of selectively operable contactmembers is as generally disclosed in the principal embodiment of thenoted application. Y

Each vertical row of stacliups comprises ten principal stackups (rstten, counting from the-front rail) and two extension stackups (theeleventh and twelfth). AS disclosed in the noted patent, each principalstacliup (see Fig. 2) has six contact pairs.

The contact bank comprises a unitary structure iii that the vertical andhorizontal conducting sttps llltl, assemble together to providestackups, extend entirely through the bank at respective intersectingdirections. Such strips are in alternate layers, and are maintained inassembled position by clamping pile up ltl, one for each support channelAs shown best in Fig. 2, each clai'nping pile up lStl comprises layersof conducting members, interspersed with insulator strips ld and toil,clamped between an upper clamp strip til and a cross-support channel 25,by screws 153 which pass through the pile up.

Each clamping pile up 15d, except the starting one (at the left of theswitch), includes six conducting strips 157 common to the staclupscomprising the vertical row immediately to the left. As disclosed in thenoted patent, such strips serve as a common multiple for the six contactmembers of all staclnips in that vertical row, for the leftwardlyoverhanging portion of the conducting strips 157, carry the fixedContact members. Each conducting strip T157 is wider than the insulatorstrips llii, and has an overlying insulator lot? which may be of thegeneral configuration as conducting strips 157. Each such strip 1157 hasa row of contact points fixed to the lower side of the overhangingleft-edge portion for cooperation, in pairs, with contact points fixedto the upper side of the ilexible traveling springs lol. The overhangingedge portion of each conducting strip and its associated overlyinginsulator ldd may be notched between tlie contact points as is disclosed.in the noted patent to facilitate observation of the contact points.

As seen best by a comparison or" Fig. l with Fig. 2, each clamping pileup i545 preceding the last, clampingly supports the base portion of thellexible Contact springs lol of the staclrups comprising a vertical row,Any such contact spring extends to the right to the vicinity of the nextsifceedinf7 clamping pile up T150, with its free end cooperativelyunderlying the overhanging left edge portion of the associated verticalmultiple strip E57, secured in the next succeeding clamping pile up.

lt will be observed' that Itwo clamping pile ups re required for firstvci al row of staclzups, the to support the base portion of the flexibleContact spring, and the second to support the vei conducting stripscomprising the contact n embers of the vertical row of stacliups. Foreach vertical row of stacliups exceeding the first, only a singleclamping pile up is req ired. Each clamping pile up between the rst andlast, supports Contact elements for the vertical rows of stacliups forthe immediately preceding vertical row, and the traveling spring contactelements for the immediately succeeding vertical row of stackups.

To facilitate spacing, the first vertical row of staclqups (to the leftas viewed in Fig. 2) is provided with dummy conducting strips 157',being of the same thickness as conductor strips l57. Insulators led',similar to insulators 160 may be of a reduced width except the lowermostinsulator Mil which is of an increased width to prevent the overlyingterminal members ll from contacting channel 25.

Traveling blades loll (Fig. l) may be formed as disclosed in the notedpatent including their integral hori- Zontal multiples Mtl. The leftportion of the strip is provided with a terminal i7@ extending beyondthe stackup 154B to facilitate external connection with the bank.

Each stackup l5@ (except the last) includes an upper guide comb 45,underlying clamping plate 151. Each upper comb l5 includes blades 46extending from the stackup and overlying each traveling blade 161 andhaving an aperture i7 for receiving the upper reduced portion 1133 ofactuating ladder H32. Each stackup l5@ also includes a lower guide comb48 having underlying blades 49 for engagement with the lower notchedportion of ladder 132 to prevent rotational movement from itsillustrated position.

Each traveling blade lol is provided with an aperture for receivingactuator 1132 which can pass therethrough edgewise. These actuatingstuds are conveniently assembled with its stackup by passing it downwardthrough the slot in the spring from above the contact bank before combd5 is assembled, and then moved forward (to the left viewed in Fig. 2)until the actuating portion 136 of ladder lEZ engages the under surfaceof its associated spring Lidl, blade lil of lower comb 48 then engagesthe lower edge of actuating stud 132. The upper end of the stud has areduced portion i333 which enters an aperture 47 in blade d6 to hold thetop of the stud in its illustrated forward position. When desired, thestud 132 may be removed by disengaging the upper and lower comb blades46 and 49 and moving the stud to the right (as viewed in Pig. 2) andupward out of the stackup.

To simplify adjustment of the contact bank, blades 46 of upper comb d5are tensioned downwardly to position the free ends of contact bladeslo?. associated therewith in engagement with an underlying insulatorlob, when in its normal relaxed position. This eliminates the expensivepreforming operation of the traveling blades lol or the individualadiustment of blades lol after the bank has been assembled to insure theunwanted metallic contact with the lixed Contact member i557 associatedwith the underlying llexible blades or channel ZS. The lower comb z3 isof relatively thin-ilexible material and blades al@ prevent studs 132from tilting out of their illustrated normal position.

Selection of the first horizontal row of stackups, for example, occursresponsive to the energization of the select magnet Mil. The underlyingwing of the associated armature, as disclosed in the noted patent, isthereby attracted upwardly into engagement with the magnet Ml wherebythe first select shaft Sll--Z is rotated in a countcrcloclwisedirection. Thereupon select levers 23%.? of shaft Sil-2, one for eachvertical row of stackups, are tipped toward a position underlying thefirst horizontal row. lncach idle vertical row of stacltups (at whichthe hold'arrnature M is in a normal position), arm ld of select lever23d, engages select lever at its mid-portion 2li?, to serve as ayielding drive means effective to drive the associated select lever,unless restrained, in onc'of its three positions (its normal position isas shown in Fig. l or to a position underlying the first or secondstackup) in response to the rotation of the select shaft in thecorresponding direction. Select levers 226) are rotatably secured toportion 92 of armature 90 by means of shoulder rivets 2id which arereceived in apertures 2lb. The select levers Edil are shown to comprisegenerally a T-structure lying in the horizontal plane.

Select levers 22%, formed of sheet metal, has two raised platforms M7and a downwardly extending stop tab Zll (Fig. 2). The portion of theselect lever 23E-i9 including elevated platforms 7 is raised to a levelwhereby it rests flatly on raised portion 95 of the armature.

When the select lever is positioned beneath the selected stackup byrotation of its associated select shaft providing the hold-magnetarmature is in its normally unoperated position, raise platforms 23W arepositioned underlying the associated actuated stud 132.

Downwardly extending tab 219 lies within the recessed portion 213 and isflanged so as to underlie the holdmagnet armature portion 9S to preventany upwarl movement of the select lever unless accompanied by itsassociated armature 9d. When the select lever is moved in eitherdirection for its selecting action, tab 219 engages the sides of therecess 213 to provide stop portions so that the select lever properlyunderlies its associated selected stackup.

When the selecting lever is moved from its normal position to one of itstwo selecting positions in response to the select shaft rotation, raisedportion 217 underlies the downwardly extended tab portion 134 ofactuating stud 132 whereby the energization of hold magnet 30 associatedwith any idle vertical row of contact stackups causes tractive portion91 to be attracted downwardly into engagement with the core of holdmagnet 80, rotating armature 90 about its pivotable mounting arrangementpreviously described. This rotating action raises portion 95 of armature90 with all its selecting levers 220. Select lever portion 217 engagesthe reduced portion 134 of stud 132 associated with the noted rststackup causing it to upwardly carry its associated stackup travelingspring 161 into engagement with its associated fixed contacts.

When the armature stroke is only partially completed, the travelingsprings 161 of the noted rst stackup engage their associated overlyingfixed Contact members 157. The nal portion of the movement of thearmature 90 causes the traveling springs to bow as contact pressureincreases. The hold magnet Si) is maintained energized as long as theconnection established is to remain intact. The select magnet M1 to M12may be deenergized immediately as disclosed in the noted patent wherebythe operated select shafts are returned to their unoperated position,the select levers 220 associated with the unoperated hold magnetarmatures are returned to their normal position. The lever 220associated with the operated armature 90 is maintained in its selectedposition by the downward pressure exerted on it by the traveling springs161 and the blade 46 of the actuated stackup. The arm of the selectfinger 130 remains in its selected position and exes as the select shaftis returned to its normal position. The select linger is returned to itsnormal position when hold magnet 80 is deenergized.

When hold magnet 80 is deenergized when the connection is released,armature 941 rotates back to its normal position against back stop screw115. The back stop position of armature 90 is readily adjusted byloosening locknut 116 and rotating the adjusting screw 115 to thedesired setting whereby locking screw 116 is then tightened. A residualclip 117 is provided, as shown in Fig. 2, and is attached to thetractive portion 91 of armature 90 to eliminate any undesirableindividual magnetism.

To facilitate armature leveling, platforms 95 are provided, one for apair of adjacent stackups; for example, a platform 95 for the stackupsassociated with select lever S1-2. This may be readily done by bendingarms 96, thereby leveling platform 95 to position its associated selectlever 220 with its overlying stud 132.

Modzyed comb constructon-Fig. 3

Referring to Fig. 3, the construction of a modied lower guide comb forthe stackup actuators will be described. The modified guide comb 48 maybe formed of relatively thin-exible material having blades 49'underlying each stackup.

The flange portion of channel 25 is provided with several oi-setportions 40 (only one of which is shown) which are received withinapertures in comb 48' to position the comb thereon. The comb may then berigidly secured to the flange as by spot-welding or riveting over theolf-set portions 49.

A modiied actuator stud 132 has a reduced lower portion 134' which isreceived within aperture 50 of blade 49 to position the lower endthereof.

While I have described above the principles of my invention inconnection with specic apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention.

I claim:

l. A contact bank comprising a succession of upstanding stackups ofcontact members arranged in a row to provide a longitudinal row ofmulti-conductor switching groups equal to one less than the number ofsaid stackups, with each switching group including exible contactmembers supported by one stackup and extending forwardly intocooperative underlying relationship with respective fixed contactmembers supported by the next succeeding stackup, each stackup includinginterspersed contact members and insulating sheets and means clampingthem together, each intermediate stackup having clamped therein the baseportions of the exible contact members which extend forwardly therefrom,with each overlaid by a xed contact member which extends rearwardly fromthe stackup for cooperation with a flexible contact member supported bythe next preceding stackup, each fixed contact member in any stackupsucceeding the first being immediately underlaid by an insulating sheetwhich is suciently narrow to provide room under the rearwardly extendingportion of such member for the free end of the cooperating flexiblecontact member held by the preceding stackup to be moved into and out ofcontact with the fixed member, the last said insulator in anyintermediate stackup being underlaid by the clamped base portion of aflexible contact member, any last said clamped base portion beingunderlaid by an insulating sheet which is widened to provide a portionwhich extends rearwardly to underlie the free end of the correspondingcontact member which extends forwardly from the next preceding stackup,whereby a definite insulated stopping barrier is provided for eachflexible contact member of the switching group in its open, or relaxed,condition, each last said insulator above the lowermost one in thestackup overlying a ixed contact member and barring contact therewith bythe free end of the flexible contact member which lies above it.

2. In a contact bank according to claim l, a separate verticallydisposed actuator for each switching group engaging the flexible contactmembers thereof near their free end and arranged and adapted to impeleach associated ilexible contact member upwardly and downwardlyresponsive to respectively corresponding movement of the actuator,separate restoring-spring means for each actuator external to the saidcontact members associated therewith normally urging the actuatordownwardly to bring the free end of the contact members into engagementwith their said underlying insulating sheets.

3. In a contact bank according to claim 1, each said stackup beingextended laterally of the said row in which they are arranged and havingadditional contact members similarly clamped between the insulatorsthereof to provide additional and similar longitudinal rows ofmulticonductor switching groups, lateral multiple conductors extendinglaterally along, and supported by, each said stackup beyond the irst andinterconnecting in common corresponding contact members in the severallongitudinal rows of switching groups, and longitudinal multipleconductors extending along the respective longitudinal rows of switchinggroups through the said stackups and between the said insulators thereofto interconnect in common corresponding contact members in the severallateral rows of switching groups.

References Cited in the lile of this patent UNITED STATES PATENTS2,577,067 Arthur Dec. 4, 1951 2,541,682 Kruithof Sept. 8, 1953 2,740,844Kruithof Apr. 3, 1956

